The invention relates to an engine cooling fan of a motor vehicle, which is provided with a dynamic unbalance compensation device.
Inertial forces or static and dynamic unbalances are generally caused by uneven mass distributions of the rotating assemblies, such as the rotor or the armature of a motor and by the fan, for example, and by geometric and positional tolerances relative to the axis of rotation and the principal axis of inertia of the drive. The geometric and positional tolerances here mean that the axis of rotation and the principal axis of inertia do not coincide. In the event of a parallel shift between the axis of rotation and the principal axis of inertia of a cooling fan with fan wheel mounted on the rotor shaft this leads to a static unbalance, for example. If the axis of rotation is tilted relative to the principal axis of inertia, on the other hand, this produces a centrifugal moment, which is equivalent in its effects to a moment disequilibrium or dynamic unbalance.
A dynamic unbalance in engine cooling fans normally gives rise to mechanical oscillations. In this case the vibrations produced can penetrate into the passenger compartment and can not only cause a steering wheel to wobble, for example, but may also give rise to unwanted vibration noises. In addition the forces generated by the dynamic unbalance are justifiably suspected of sporadically giving rise to rapid bearing wear in engine cooling fan motors.
In modern engine cooling fans the static unbalance is generally compensated for in order to adhere to admissible limits. Compensating for the dynamic unbalance in fans which are often of a very flat construction, however, turns out to be a difficult and very intricate process.